Method of and apparatus for drying, conditioning, and regulating tee moisture content of hygroscopic materials



W. H. CARRIER. METHOD OF AND APPARATUS FOR DRYING, CONDITIONING, AND REGULATING THE MOISTURE CONTENT OF HYGROSCOPIC MATERIALS.

AHLICATIUN FILE!) MAR. 27, 1917.

Patented Oct. 11, 192L 3 SHEETS-SHEET 1.

ElZ'IIIi-"M "WP/6 N 5 fnumfon fl/ o/wy w. H. CARRIER. METHOD OF AND APPARATUS FOR DRYING, CONDITIONING, AND REGULATING THE MOISTURE CONTENT OF HYGROSCOPIC MATERIALS.

APPLICATION FILED MAR. 27. 1911.

1,393,086, Patented Oct. 11, 1921.

3 SHEETSSHEET 2.

1 I I II I I; MIR III T; Thumnsht- W. H CARRIER. METHOD OF AND APPARATUS FOR DRYING, CONDITIONING, AND REGULATING THE MOISTURE CONTENT OF HYGROSCOPIC MATERIALS. APPLICATION FILED MAR. 21. 1917.

1,393,086. Patented Oct. 11, 1921.

3 SHEETSSHEET 3- 1 UNITED STATES) WILLIS H. CARRIER,

PATENT OFFICE.

0F BUFFALO, NEW Y/ORK, AssIenoR T0 CARRIER ENGINEERING- CORPORATION, OF BUFFALO, NEW YORK. I

METHOD OF AND APPARATUS FOR DRYING, CONDITIONING, AND REGULATING TEE MOISTURE CONTENT OF HYGROSCOPIC MATERIALS.

Specification of Letters Patent.

Patented Oct. 11, 1921.

Application filed March 27, 1917. Serial No. 157,674.

To all whom it may) concern:

Buffalo, in. the county of Erie and State of,

New York, have invented a new and useful Improvement in Methods of and Apparatus for Drying, Conditionin and Regulating the Moisture Content of l lygroscopic Materials, of which the following is a specification.

Many products are very easily injured in conditioning, or drying, heating, or cooling the same by a too rapid or non-uniform drying or treatment in which the outer portion or certain exposed portions of the materials are dried, heated or cooled to a much greater extent than the interior or less exposed portions. Macaroni and tobacco are examples of such products. In drying macaroni, for instance, a too rapid drying of the outer surface causes the product to crack and break, thereby destroying its commercial value. Similarly in the curing or drying of green tobacco, a too rapid drying in the first stages kills the living cells before they have undergone the period of starvation which is required to convert the.

starch into sugar, and later on in the process, for certain grades of tobacco at least, the drying requires to be modulated for the best results in order to oxidize the sugarformed in the previous step and to bring about the desired light brown shade which is required in the highest grades. In the final steps of drying these products and other similar products, it is necessary to the attainment of the best results to dry the product to a uniform degree throughout andyet retain a uniformly distributed final percentage of moisture to 've the products their natural elasticity an retain the other properties which are dependent in a large degree upon the hygroscopic condition of the products.

To accomplish all this satisfactorily, I have found that three conditions are important:-

First to maintain a moist atmosphere of regulated temperature and humidity about the material, which conditions can be varied in the process of drying at various stages, as required in the proper manipulation of each particular product. 7

Second, theremust be a thorough and uniform circulation of air over all portions of the material being treated and any air being introduced into the treating chamber should not come into direct contact with the material except it first be thoroughly mixed with the air surrounding the material so as to homogenize it with respect to temperature and humidity.

Third, it is necessary that the temperature and moisture content of the air be uniform throughout the drying chamber so that some of the material shall not dry too fast while other portions of the material dry too slowly. This requires that the air while passing over the material shall not be greatly changed in moisture content and temperature due to the absorption of moisture from the material with the consequent lowering of the temperature. To insure this result, the circulation through the material should be relatively rapid and the rate at which the moisture is given ofi from the material relatively slow.

Ilniformity of air conditions could be secured by handling an excessively large volume of air and passing it through the material only once and then reconditioning it by a separate apparatus, but this would mean the conditioning of a very large volume of air and would entail a great expense in the cost of apparatus and in the cost of operation.

The object of this invention is to produce a method and apparatus by which all of these desirable results in the conditioning of materials with respect to their moisture content and also in the heating'or cooling of materials may be secured in an economical and practicable manner without passing the entiresupply of air through an apparatus tobe conditioned, but only a very small portion of it. This air which is conditioned and supplied to the chamber in which the material is treated may be taken allfrom the outside or it may be entirely return air from the chamber in certain ste s of the process, or it may be partly,outsidia air and partlyreturn air from the chamber.

In accordance with this method, a secondary current of air of relatively large volume is caused to circulate through the material by induction which is produced by discharging a relatively smaller volume of conditioned air into the chamber containing the material through a series of nozzles or re- I stricted openings.

- the chamber with tion introduced in relatively small volume downwardly through that the proper temperature and humidity desired in the chamber is maintained. The quality of the air introduced is varied in such a way as to balance the moisture given off or absorbed by the material with a corresponding drop or rise in the temperature produced relatively by such processes. Thus, in drying material, the air is introduced at a lower moisture content and preferably at a higher temperature than the air in the chamber, while in adding moisture to the material, as is usually required in the last process of drying and conditioning, the air is introduced at a higher moisture content and at a lower temperature than the condition maintained in the chamber.

Usually and preferably the material is placed in the chamber so as to leave a space in the'chamber at opposite sides of and above the material, and the air is discharged through a row or series of nozzles or outlets near the ceiling at one side of the chamber and blown horizontally directly beneath the ceiling toward the far side of the chamber, while the air is removed or escapes from thechamber through an exhaust duct or openings preferably located at the same side of the chamber as the supply nozzles and underneath the same either adjacent thereto or at the floor line, as preferred. The space about the material should be practically free from obstructions and should have an area approximately equal tothe free area for air passage through the material and the material should be hung in rows, placed on trays or otherwise disposed, with the air passages through the same parallel to the direction in which the air is blown. The effect of this arrangement is to induce a large volume of air, usually three to four times the volume of air discharged into the chamber, to circulate and thoroughly mix with the intro duced air in the middle space between the material and the ceiling. It then passes the free space at the far side of the chamber, thence substantially horizontallythrough the material and thence upward through the free space at the inlet side ofthe chamber where a portion of it passes out through the exhaust duct but the greater part again returns to the space above the material where it again is mixed with the air discharged from the nozzles. It will thus be seen that the material is subjected only to the secondary and return air current which is flowing in an opposite direction to the direction of discharge from the nozzles. This I effects a very uniform distribution through all portions of the material and secures an equally uniform distribution of temperature. As a result, the temperature and the hygroscopic condition of the material, whether in drying or in moistening is effected uniformly throughout all parts of the material, which has always previously been very difficult, if not impossible to secure.

Any other disposition of the parts, giving a similar relative arrangement of the air ducts and spaces could be used. The middle space may either be located horizontally at the ceiling or at the floor with the air outlets blowing horizontally, or at one side of the chamber with the air outlets blowing vertically downwardly or upwardly, or at one side of the chamber with the outlets blowing horizontally, the relative arrangement in all these cases being substantially the same.

The temperature and humidity of the air in the room are regulated under the control of a thermostat and hygrostat or wet bulb thermostat as hereinafter described.

Apparatus suitable for carrying out the above method are illustrated in the accompanying drawings, in which,

I Figure 1 is a sectional plan view of one form of apparatus.

Fig. 2 is a longitudinal sectional elevation thereof on line 2-2, Fig. 1.

Fig. 3 is a transverse sectional elevation thereof on line 3-3, Fig. 1.

Fig. 4 is a section of the chamber showing the apparatus in end elevation.

Fig. 5 is a transverse sectional elevation showing a double arrangement of the apparatus in which the air ducts are arranged to simultaneously treat material located at opposite sides thereof in the chamber.

Referring first to Figs. 1 to 4 of the drawings, A represents the room or chamber in which the material is located, and B the material. The material is placed so as to leave spaces 10, 11 and 12 in the chamber on three sides of the material, preferably at opposite sides and above the material, as before explained.

13 indicates an air supply duct extending along one side of the chamber near the ceiling and having nozzles or restricted outlets 14 through which the air is discharged horizontally into the space 11 above the material toward the far side of the chamber, and 15 represents an air exhaust duct which. as shown, extends parallel with and just below the supply duct and has openings 16 in its bottom for the escape of air from the chamber. These ducts are located in or adjacent to the upper part of the s ace 10 at one side of the material. A fan 1 delivers air at a suitable pressure to the supply duct13 and in the apparatus show ii, this fan is also connected to the exhaust duct 15 and serves to exhaust the air from the chamber A. A separate exhaust fan could be used, but a separate fan is only necessary in large installations or exceptional cases. The material shown is hung on racks 18 or otherwise supported by means arranged so as to leave air passages 19 extending between the racks parallel to the direction in which the air is discharged by the nozzles 14. The air discharging from the nozzles induces a circulation of the/air in the chamber in the direction indicated by the arrows in Fig. 3, the air passmaterial, thence downwardly in the space 12 at the far side of the chamber, thence horizontally through the material in the passages 19 and thence upwardly in the space 10 to again miX with the incoming air in the space 11 and be recirculated. Part of the air passes out from the space 10 through the exhaust duct. The middle space 11 thus serves as an induction and mixing space, the space 12 farthest from the supply duct as a plenum or pressure chamber, while the space 10 adjacent to the supply duct is a vacuum or exhaust space.

Preferably the material is disposed as clearly shown in the drawings, in horizontal tiers one above the other with horizontal free 1 air spaces or passages between the tiers. The upright air passages or interstices 19 in the material communicate with these horizontal spaces and also communicate at their upper ends with the air space 11 above the ma terial. The disposition of the material in this way insures a practically equal drying effect throughout the material from top to bottom thereof. The cooler moist air settles toward the floor of the chamber but the circulation is more active near the floor and thus equalizes the drying effect. The communication of the upper ends of the upright passages 19 with the air space 11 above the material permits air eddies in the upper portion of the material which increase the drying effect in, the upper portion where the horizontal circulation of the air through the material is not so active.

The moisture content, and preferably the temperature also of the air discharged into the chamber are varied for controlling the temperature or humidity, or both, in the chamber A, as required. For this purpose the following means are preferably employed. 20 indicates dampers controlling the' ing horizontally in the space 11 above the ber A or in the return air duct so as to be governed by the humidity conditions in the chamber. The air introduced into the chamber may be all fresh air, all return air or a properly proportioned mixture of fresh and return air, depending upon the operation of the dampers. For instance, the hygrostat'24 controls a damper actuating motor 25 operatively connected to the dampers 20 and 23, so as to open the fresh air dampers while closing the return air dampers and vice versa. 26 indicates dampers controlling a relief opening for the return or exhaust duct 15. These dampers are connected to the return air dampers so as to open when the latter close and close when the return dampers open. Additional moisture may also be supplied to the air when this is necessary to secure a required humidity in the chamber by any suitable means, such as a steam jet 27 which is arranged to discharge into the air inlet trunk 21 and, is operated by a diaphragm valve 28 controlled by the hygrostat or web bulb thermostat 24. Where additional humidity is required with a low temperature, water can be used instead of steam and in cases where very low temperatures or very low humidities are required, refrigeration can be used to reduce the moisture still further.

.29 represents a heater of any suitable sort and located in any suitable way for heating the air before it is discharged into the chamber to raise the temperature in the chamber. A steam heater located in the air inlet trunk 21 is shown, the steam being turned on and off by a diaphragm valve 30 controlled by a thermostat 31, which may be suitably located in the chamber A or in the return air duct 15. The hygrostat 24 and thermostat 31 are set in accordance with the hygrometric and temperature conditionsmequired in the chamber and operate automatically through the instrumentalities described to maintain such conditions. The control temperatures and humidities can be adjusted at different points in different steps of the drying or conditioning, as found necessary through experience with each particular product.

Other suitable instrumeritalities for regu lating the temperature and humidity conditions in the chamber in accordance with the requirements of the material being treated could be employed, but the described means have been found very eflicient in use.

Instead of heating the air before it is introduced into the chamber, the required temperature in the chamber could be secured by other suitable means. Y

In the apparatus shown in Fig. 5, the material B is arranged in the chamber A in two portions separated by an intervening free space 10 in the middle of the chamber and the air supply duct 13 is located along the middle of the cha ber above this space and has restricted noz les arranged to disrections toward the opposite sides of the chamber. The exhaust duct 15 is also located in the space 10 at the floor line. In this arrangement free spaces 11 are left in the chamber above each portion of the material and a free space 12 is provided between each portion of the material and the adjacent side wall of the chamber, the spaces .10, 11 and 12 corresponding respectively with the spaces 10, 11 and 12 in the first construction described. Open ended tubes 32 are shown in this arrangement located so that the air will be discharged from the supply nozzles 14* through these tubes. The nozzles and tubes thus operate as aspirators and effect avery efiicient circulation of the induced current of air. These aspirator tubes can also be used, if desired or necessary in the apparatus first described. The induced air currents circulate in the directions indicated by the arrows passing over the material in the spaces 11*, thence downwardly in the spaces 12 and thence horizontally through the material and upwardly in the exhaust space 10, part of the air escaping through the exhaust duct in the same manner as in the first described arrangement. r

I claim as my invention 1. The hereindescribed method of regulating the physical condition of materials, consisting in disposing the material in a chamber so as to leave substantially unobstructed connecting. spaces in the chamber at three adjoining sides of the material, two of which sides are opposite each other and are connected by the third side, and so as to provide air flow passages through the material, and discharging air into an unobstructed space of the. chamber so as to fiow through the middle one of said spaces in a direction substantially parallel with said third side of the material and at a velocity such as to induce the circulation of a relatively larger volume of other air in the chamber and induce the flow 8f the circulating mixed air through said flow. passages in the material.

2. The hereindescribed method of regulating the physical condition of materials, consisting in disposing the material in a chamber so as to leave substantially unobstructed connecting spaces in the chamber at three adjoining sides of the material, two of which sides are oppositeeach other and are connected by the third side, and so as toprovide air flow passages through the material extending in a direction from one to the other of said opposite sides, and discharging air into an tz'nol structed space of the chamher so as to fiow through the middle one of said spaces in a direction substantially parallel with saidfiow passages in the material and at a velocity such as to induce the circulation of other air in the chamber and incharge the air horizontally in opposite di-:1'I duce the flow of the circulating mixed air through said flow passages in the material in a direction substantially opposite to that in which the air is discharged into the chamber.

3. The hereindescribed method of regulating the physical condition of materials, consisting in disposing the material in a chamber so as to leave substantially unobstructed connecting spaces in the chamber at three adjoining sides of the material, two of which sides are opposite each other and are connected by the third side, and so as to provide air flow passages through the material extending in a direction from one to the other of said opposite sides, discharging air into an unobstructed space of the chamber so as to flow through the middle one of said spaces in a direct on substantially parallel with said flow passages in the-material and at a relatively high velocity, and withdrawing air from the chamber adjacent that side of the material at which the air is discharged into the chamber, whereby the circulation of 'a relatively larger volume of other air in the chamber is induced, the incoming air mixes and circulates with the other air before flowing through the material, and the circulating mixe air is caused to flow through the material.

4:. The hereindescribed method of regu lating the physical condition of materials, consisting in disposing the material in a chamber so as to leave substantially unobstructed connecting spaces in the chamber at opposite sides of and above the material and so as to provide air flow passages through the material extending in a direction from one to the other of said opposite sides, discharging air at a relatively high velocity into an unobstructed space of the chamber adjacent one of said sides of the material and in a direction so as to flow substantially horizontally through said space above the material toward said opposite side of the material, and withdrawing air from' the chamber adjacent that side of the material at which the air is discharged into the chamber, thereby inducing the circulation of a relatively larger volume of other air in the chamber, and inducing the flow of the circulating mixed air through said flow passages in the material. Y

5. The hereindescribed method of regulating the physical condition of materials, consisting in disposing the material in a chamber so as to leave substantially unobstructed connecting spaces'in the chamber at opposite sides of and above the material and so as to provide air flow passages extending through the material from one to the other of said opposite sides and communicating at their tops with said space above the material, discharging air at a relatively high velocity into an unobstructed space of the chamber adjacent one of said opposite sides of the material and in a direction so as to flow substantially horizontally through said space above the material toward said opposite side of the material, and withdrawing air from the chamber adjacent that side of the material at which the air is discharged into the chamber, thereby inducing the circulation of a relatively larger volume of other air in the chamber and inducing the flow of the circulating mixed air through said flow passages in the material.

6. The hereindescribed method of regulating the physical condition of materials, consisting in disposing the material in a chamber so as to leave substantially unobstructed connecting spaces in the chamber at opposite sides of and above the material and so as to provide horizontal free air passages through the material extending in a direction from one to the other of said opf posite sides and vertical air passages in the material connecting with said horizontal air passages discharging air at a relatively high velocity into an unobstructed space of the chamber adjacent one of said sides of the material and in a direction so as to fiow substantially horizontally through said space above the material toward said opposite side of the material, and withdrawing air from the chamber adjacent that side of the mate rial at which the air is discharged into the chamber, thereby inducing the circulation of a relatively larger volume of other air in the chamber, and inducing the flow of the circulating mixed air through said flow passa es in the material.

The hereindescrihed method of regulating the physical condition of materials, consisting in disposing the material in a chamber so as to leave substantially unobstructed connecting spaces in the chamber at three adjoining sides of the material, two of which sides are opposite each other and are connected by the third side, and so as to provide air flow passages through the material, and discharging air into an unobstructed space of the chamber so as to flow through the middle one of said spaces in a directlon substantially parallel with said third side of the material and at a velocity such as to induce the circulation of a relatively larger volume of other air in the chamber and induce the flow of the circulating mixed air through said flow passages in the material, and regulating the condition of the relatively small volume of incoming air prior to its introduction into the chamber so that when said air mixes with the other air in the chamber, the mixed air will have the required condition for the e m nt of the material.

8. The hereindescribed method of regulating the physical condition of materials, consisting in disposing the material in a chamber so as to leave substantially unobstructed connecting spaces in the chamber at three adjoining sides of the material, two of which sides are opposite each other and are connected by the third side, and so as to provide air flow passages through the material extending in a direction from one to the other of said opposite sides, discharging air into an unobstructed space of the chamher so as to flow through the middle one of said spaces in a direction substantially parallel with said flow passages in the material and at a relatively high velocity, withdrawing air from the chamber adjacent that s1de out the material at which the air is discharged into the chamber, whereby the circulation of a relatively larger volume of other air in the chamber is induced, the incoming air mixes and circulates with the other air before flowing through the material and the circulating mixed air is caused to flow through the material, and regulating the condition of the relatively small volume of incoming air prior to its introduction into the chamber so that when said air mixes with the other air in the chamber, the mixed air will have the required condition 'for the treatment of the material.

9. In an apparatus for the purpose described, the combination of a chamber, means for supporting the material in the chamber so as to leave connecting substantially unobstructed spaces in the chamber at three adjoining sides of the material, two of which sidesare opposite each other and connected by the third side, and so as to provide air flow passages through the material, means constructed and arranged to discharge air at a relatively high velocity into the chamber adjacent one end of the middle one of said spaces and so as to flow through said middle space substantially parallel with said third side of the material, and means for the escape of air from the chamber adjacent that side of the material at which the air is discharged into the chamber, whereby the circulation of a relatively larger volume of other air in the chamber is induced, the incoming air mixes and circu lates with the other air before flowing through the material, and the circulating mixed air is caused to flow through the'material.

10.'In an apparatus for the purpose described, the combination of a chamber, means for supporting the material in the chamber so as to leave connecting substantially unobstructed spaces in the chamber at three adjoining sides of the material, two of which sides are opposite each other and connected by the third side, and so as to provide air flow passages through the material extending in a direction from one to the other of said opposite sides, nozzles located adjacent one end of the middle one of said spaces and arranged to blow a1r at a relatively high velocity througlr said middle space in a direction substantially parallel with said flow passages in the material, and means for the escape of air from the chamber adjacent that side of the material at which the air is discharged into the chamber, whereby the circulationof a relatively larger volume of other air 1n the chamber is induced, the incoming air mixes and circulates with the other air before flowing through the material, and the circulating mixed air is caused to flow through the material.

11. In an apparatus for the purpose described, the combination of a chamber, means for supporting the material in the chamber so as to leave connecting substantially unobstructed spaces in the chamber at opposite sides of and above the material and so as to provide air flow passages through the material extendingin a direction from one to the other of said opposite sides and communicating at their tops with said space above the material, means constructed and arranged to discharge air at a relatively high velocity into the chamber adjacent one end of the middle one of said spaces and so as to flow through said middle space substantially parallel with said third side of the material, and means for the escape of air from the chamber adjacent that side of the material at which the air is discharged into the chamber, whereby the circulation of a relatively larger volume of other air in the chamber is induced, the incoming air mixes and circulates with the other air before flowing through the material, and the circulating mixed air is caused to flow through the material.

12. In an apparatus for the purpose described, the combination of a chamber, means for supporting the material in the chamber so as to leave connecting substantially unobstructed spaces in the chamber at three adjoining sides of the material, two of which sides are opposite each other and connected by the third side, and so as ,to provide air flow passages through the material, means constructed and arranged to discharge air at a relatively high velocity into the chamber adjacent one end of the middle one of said spaces and so as to flow through said middle space substantially parallel with said third side of the materiahmeans for the escape of air from the chamber adjacent that side of the material at which the air is discharged into the chamber, whereby the circulation of a relatively larger volume of other air in the chamber is induced, the incoming air mixes and circulates with the 65 other air before flowing through the material, and the circulating mixed air is caused to flow through the material, and means for regulating the moisture content of the incoming air prior to its introduction into the chamber to produce a definite humidity condition in the chamber.

13. In an apparatus for the purpose described, the combination of a chamber, means for supporting the material in the chamber so as to leave connecting substantially unobstructed spaces in the chamber at three adjoining sides of the material, two of which sides are opposite each other and connected by the third side, and so as to provide air flow passages through the material, means constructed and arranged to discharge air at a relatively high velocity into the chamber adjacent one end of the middle one of said spaces and so as to flow through said middle space substantially parallel with said third side of the material, means for the escape of air from the chamber adjacent that side of the material at which the air is discharged into the chamber, whereby the circulation of a relatively larger volume of other air in the chamber is induced, the incoming air mixes and circulates with the other air before flowing through the material, and the circulating mixed air is caused to flow through the material, and means for regulating the moisture content and temperature of the incoming air prior to its introduction into the chamber to produce'a definite humidity and temperature condition in the chamber.

14. In an apparatus for the purpose described, the combination of a chamber, means for supporting the material in the chamber so as to leave connecting substantially unobstructed spaces in the chamber at three adjoining sides of the material, two of which sides are opposite each other and connected by the third side, and so as to provide air flow passages through the material, means constructed 110 and arranged to discharge air at a relatively high velocity into the chamber adjacent one end of the middle one of said spaces and so as to flow through said middle space substantially parallel with said third 115 side of the material, means for the escape of air from the chamber adjacent that side of the material at which the air is discharged into the chamber, whereby the circulation ofa relatively larger volume of 120 other air in the chamber is induced, the incoming air mixes and circulates with the other air before flowing through the material, and the circulating mixed air is caused to flow-through the material, automatic 125 means controlled b the humidity in the chamber for regulatmg the moisture content of the incoming air prior to its introduction into the chamber, and means for regulating the temperature in the chamber.

15. In an apparatus for the purpose described, the combination of a chamber, means for supporting the material in the chamber so as to leave connecting substantially unobstructed spaces in the chamber at three adjoining sides of the material, two of which sides are opposite each other and connected by the third side, and so as to provide air flow passages through the material, means constructed and arran ed to discharge air at a relatively high velocity into the chamber adjacent one end of the middle one ofsaid spaces and so as to flow through said middle space'substantially parallel with said third side of the material, means for the escape of air from the chamber adjacent that side of the material at which the air is discharged into the chamber, whereby the circulation of a relatively larger volume of other air in the chamber is induced, the incoming air mixes and circulates with-the other air before flowing through the material, and the circulating mixed air is caused to flow through the material, and automatic means controlled by the humidity and temperature in the chamber for regulating the moisture content and temperature of the incoming air prior to its introduction into the chamber.

16. In an apparatus for the purpose described, the combination of a chamber,

means for supporting the material in the chamber so as to leave connecting substantially unobstructed spaces in the chamber at three adjoining sides of the material, two of which sides are opposite each other and connected by the third side, and so as to provide air flow passages through the material extending in a direction from one to the other of said opposite sides, nozzles located adjacent one end of the middle one of said spaces and arranged to blow air at a relatively high velocity through said middle space in a direction substantially parallel with said flow passages in the material, open ended tubes through which the air is discharged by said nozzles, and means for the escape of air from the chamber adjacent that side of the material at which the air is discharged into the chamber, whereby the circulation of a relatively larger volume of other air in the chamber is induced, the incoming air mixes and cir-- culates with the other air before flowing through the material, and the circulating mixed air is caused to flow through the material.

Vl77itness my hand this 24 day of March, 191

WILLIS H. CARRIER. Witnesses:

M. J. PITMAN, C. W. PARKER. 

